Juniper (Juniperus virginiana) encroachment into grassland results in increased trace-element inputs

Abstract

Background and aims Woody plant encroachment poses a significant threat to grasslands globally, and in the southcentral USA, juniper (Juniperus virginiana) is rapidly taking over large areas of grasslands. Despite ongoing research, the reasons behind the rapid encroachment of juniper species in Oklahoma remain elusive. We hypothesized that the interaction between juniper canopy, aeolian, and wet-deposition processes lead to a modification in trace-element inputs through stemflow and throughfall. This, in turn, plays a crucial role in determining the success of juniper encroachment. Methods We measured the influx of trace-elements in stemflow and throughfall beneath juniper canopies of different sizes, contrasting the results with those obtained under ambient precipitation. Results Our research unveiled a significant influence of the juniper canopy on trace-element inputs via stemflow and throughfall. Specifically, there was a significant increase in manganese, boron, and chlorine inputs, coupled with a decrease in copper inputs. Additionally, there was an increase in most cations and sulfate. Results Our results indicate that juniper encroachment alters the profile of trace-element, cation, and anion inputs beneath their canopies. Increased levels of manganese and reduction of copper inputs into the ecosystem may enhance the juniper growth, creating a positive feedback mechanism that could contribute to the success of juniper and other woody encroachers.